The typical squelch circuit cuts off

Solution (By Examveda Team)

Squelch Circuit Definition:
A squelch circuit is a noise reduction feature in a radio receiver. Its primary function is to mute the receiver's audio output when no valid signal is present, preventing the listener from hearing unwanted background noise or static.

Correct Answer: A
Option A: an audio amplifier when the carrier is absent is correct. The squelch circuit operates by monitoring the received signal strength. When a carrier signal (the transmitted signal carrying the information) is absent, indicating no valid transmission, the squelch circuit activates and cuts off the audio amplifier. This prevents the background noise from being amplified and heard by the user. The audio amplifier remains muted until a sufficiently strong carrier signal is detected.

Why other options are incorrect:
Option B: RF interference when the signal is weak is incorrect. While a squelch circuit can help to some extent with weak signal interference, its primary function is not to eliminate RF interference directly. It mainly focuses on silencing the receiver's audio output in the absence of a carrier. RF interference is addressed through other means like filtering and proper antenna design.

Option C: An IF amplifier when the AGC is maximum is incorrect. The Automatic Gain Control (AGC) adjusts the amplification of the Intermediate Frequency (IF) amplifier to maintain a relatively constant output signal level. The squelch circuit's operation is independent of the AGC's function. It doesn't directly control IF amplification based on AGC levels.

Option D: An IF amplifier when the AGC is minimum is incorrect. Similar to option C, the squelch circuit's operation is not directly tied to the AGC level in the IF amplifier. A minimum AGC indicates a weak signal, but the squelch circuit's decision to mute the audio is based on the presence or absence of a carrier, not solely on the AGC level.